Defence Science Journal, Vol. 68, No. 6, November 2018, pp. 566-571, DOI : 10.14429/dsj.68.12669  2018, DESIDOC

Internet of Things Controlled Reconfigurable for RF Harvesting

V. Arun* and L.R. Karl Marx# *Department of Electronics and Communication Engineering, Anna University Regional Campus, Madurai - 625 019, India #Department of Electronics and Communication Engineering, Thiagarajar College of Engineering, Madurai - 625 019, India *E-mail: [email protected]

ABSTRACT Internet of Things (IoT) controlled a reconfigurable antenna with PIN diode switch for modern communication is designed and implemented. Direct contact of biasing network with the antenna is eliminated and the switching unit is manipulated through IoT method. The proposed antenna has ring structures, in which the outer ring connects the inner ring structure through a PIN diode switch. The dimension of the proposed antenna is reported as 50 mm × 50 mm and its prototype has been made-up on epoxy-Fr4 substrate with 1.6 mm thickness. This antenna setup is made to reconfigurable in four bands (4.5 GHz, 3.5 GHz, 2.4 GHz, and 1.8 GHz) through switching provided by IoT device (NodeMCU). The antenna has a good return loss greater than -10dB.In switching state 2 the antenna has a return loss of -30 dB peak is attained at 3.4 GHz of operating frequency. Similarly the gain response of antenna is good in its operating bands of all switching states and obtained a maximum gain of 2.7 dB in 3.5 GHz. Bidirectional is obtained in all switching states of the antenna. Keywords: Reconfigurable antenna; Internet of Things antenna; PIN diode switching antenna; Frequency reconfiguration; RF Harvesting

Nomenclature of the Antenna can be controlled by programming the Area of the ring structure a microcontroller9. The RF Energy harvesting using the Antenna frequency F reconfigurable antenna is an uptrend research area. In addition FR4substrate thickness h to that energy harvesting this micro controller programmed ε Relative permittivity r antenna can auto fit to the remote location for the RF Energy 5,10 Resonant frequency fr harvesting persistence . Dual tone RF harvesting antenna is discussed; it harvests in GSM and UMTSb and. But it’s bulky 1. INTRODUCTION in size due to Yagi antenna array11. In these existing techniques Modern communication devices are supported by the controlling of antenna and switching should done with a more than one service and are extensively must for today’s manual connectivity to micro-controller. The IoT controlled communication1. Reconfigurable antenna is a perfect entrant to Reconfigurable antenna eliminates the human assistance and meet such demand in today’s communication. Reconfigurable function the antenna switching. antennas are categories based on: Polarisation reconfigurable2, This paper presents the NodeMCU (ESP8266) as a device pattern reconfigurable3, and frequency reconfigurable4. This to achieve the IoT controlled reconfigurable antenna. Also it is reconfigurability is achieved by altering the physical structure employed as a switching element in the PIN Diode. of the antenna that is by connecting or disconnecting the radiating elements of antenna structure5. Various switching 2. DESIGN PROCEDURE OF RING ANTENNA techniques are employed for reconfiguration that are provided The basic shapes of microstrip patch antennas are found to by devices such as PIN diode, varactor diode, MEMS switched be rectangular15, triangular and circular. Among these circular/ and photoconductive switches6. Reconfigurable antenna annular ring shape antenna is analysed and found to be simple design with PIN diode and varactor diode requires external and better with respect to multiband frequency operation and in cable connection to provide DC bias to the lumped elements7. placement of feed point16. The Antenna has simple monopole Though the MEMS switches provides high isolation between ring structure that is fed by microstrip technique with the lumped elements and DC biasing circuitry, the switching length of 11 mm and width 4 mm. It consists of three layers: speed is very low compared to other switching mechanism8. The upper radiation patch, the inner substrate that is made up Micro-controller switching mechanism makes more time of epoxy-FR4 material of thickness 1.6 mm and the bottom efficient without any human hindrance. The reconfigurability . The upper and bottom layer of antenna is made up of copper material of thickness 0.04 mm. The inner and Received : 05 February 2018, Revised : 06 September 2018 outer diameter of the first ring is 34 mm and 38 mm and the Accepted : 10 October 2018, Online published : 31 October 2018

566 Arun & Marx : Internet of Things Controlled Reconfigurable Antenna for RF Harvesting second ring is 22 mm and 26 mm, respectively. Both the rings The prototype model testing is made with Vector Network are connected in the upper side with a square patch of 4 mm × Analyser (VNA) of 0 - 18 GHz. 4 mm. The antenna ground is taken to be 50 mm × 50 mm to The equivalent circuit of the ring antenna will consist of allow radiation above and below the substrate is described in lumped values of ground, PIN diode and radiating element of the Table 1. ring patch structure. This combined element of ring shaped antenna consists of parallel and series combination of RLC Table 1. Details of length and width of the antenna elements. At ON state of this antenna’s reconfigurable switching Ring antenna (Parameters) Dimension (mm) process the capacitance of respective PIN diodes (D1, D2) are Patch length 50 getting cancelled. Patch width 50 3. IoT SWITCHING Outer ring diameter 38 Switching for this antenna is provided by PIN Diode which Inner ring diameter 26 is controlled by NodeMCU unit as like the micro-controller Centre patch diameter 10 switching device3. The block diagram for IoT based switching Feed length 11 of Ring Antenna with the help of PIN Diode switches is shown Feed width 4 in the Fig. 3. The NodeMCU switches the Diodes D1 and D2 as per the software programmed in it. Ground plane length 50 The Biasing voltage from the NodeMCU can switch on and Ground plane width 50 off the D1 and D2 PIN diodes. Based on the diode switching of FR4 Substrate thickness 1.6

The antenna is designed with the help of circular dimension equation as follows12. F a = (1) 1 2hFΠ 2 1++ ln 1.7726 Πε Fh2 r 

8.791*109 F = (2) f ε (a) (b) rr Figure 1. Antenna layout: (a) Top view and (b) Bottom view (all dimensions are in mm). where a is area of the ring structure and F is antenna frequency. The substrate FR4 thickness and relative permitivity is denoted as h and ε correspondingly. After r including the fringing effect of the circular patch antenna, the effective radius a( e) of the patch antenna is derived from the Eqn. (3) as follows, 1 2haΠ 2 a =+1 ln+ 1.7726 (3) e Πε ah2 r With the assistance of Eqn. (3) the resonant frequency

(fr) of the antenna is derived as per the Eqn. (4) (a) (b) 1.8412ν 0 Figure 2. Prototype design of ring antenna with PIN diodes D1 and (f ) = (4) D2 (a) Front view (b) Back view. r 110 2Πεa er

The outer ring patch is connected to the inner ring patch with PIN diode D1 and the inner ring is in contact with the center circular patch with PIN Diode D2. Here in this proposed work SOD323 PIN diodes are used, which provides switching to the reconfigurable antenna. The antenna is simulated using HFSS simulator tool and the switching is provided using Lumped RLC boundary. The detail Figure 3. Block diagram of IoT based reconfigurable ring layout structure of antenna is as shown in the Fig. 1. antenna.

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ON and OFF, the flow of RF signal through the Ring Antenna is varied and the different band of operating frequencies can be achieved. The NodeMCU unit itself consists of WiFi based connectivity with the Internet. This combined reconfigurable antenna and NodeMCU unit control, change of program and monitor through World Wide Web. The prototype model of PIN diode embedded Reconfigurable Ring shaped antenna is connected with the IoT device (NodeMCU) is as shown in above Fig. 4.

Frequency (GHz) (a)

Frequency (GHz) Figure 4. IoT device connected with the ring antenna. (b) Figure 5. measured and simulated return loss: (a) state 1 and 4. RESULTS AND DISCUSSION (b) state 2. The proposed IoT-based reconfigurable antenna is designed and validated using HFSS software. In the experimental measurement PIN diodes used as a switching element and the Prototype antenna results are obtained with VNA. When the D1 and D2 is in off state the antenna operates in the frequency band of 2 GHz to 5 GHz and suitably providing peak response (fp) in 4.5 GHz frequency range, this is considered as a state ‘0’ of the antenna and the results are as shown in the Fig. 5(a). In the state ‘1’, the D1 is in on condition while the D2 is remains off condition, and the obtained frequency range of 2 GHz to 3.7 GHz and concentrates on 3.5 GHz band is as shown in Fig. 5(b). As shown in the Fig. 6(a) the return loss results for stage Frequency (GHz) 3, where the diodes D1 and D2 is in OFF and ON conditions (a) respectively. Here in this state the operating frequency ranges from 1.8 GHz to 3.4 GHz, and it focuses the 2.4 GHz Band. In state 4 both the diodes are in ON condition and the results as shown in Fig. 6(b). In this state the frequency ranges from 1 GHz to 3.7 GHz and it concentrates on the 1.8 GHz band. There is a discrepancy between simulated and measurement results due to switch installation and measuring environment. The comparison table for the four switching states diode’s condition, its working/ resonant frequency range and bandwidth for the appropriate states of the antenna is as given in Table 2. The radiation pattern in E-plane (i.e. X-Z plane represented in brown colour) and the radiation pattern in H-plane (i.e. Y-Z plane represented in red colour) at 2.4 GHz in OFF state and Frequency (GHz) 3.2 GHz and 4.5 GHz in ON state is revealed in the Figs. 7(a), (b) 7(b) and 7(c). The radiation pattern remains same for all the Figure 6. measured and simulated return loss: (a) state 3 and (b) state 4.

568 Arun & Marx : Internet of Things Controlled Reconfigurable Antenna for RF Harvesting

(a) (b) (c) Figure 7. Radiation pattern: (a) state 1, (b) state 3, and (c) state 4. Table 2. Comparison of Four switching states Antenna PIN Diode Working/ resonant Bandwidth switching states D1 D2 frequency (GHz) (GHz) 0, 0 OFF OFF 2 - 5 3

(state 1) (fp = 4.5) (dB)

0, 1 OFF ON 2 - 3.7 1.7

(state 2) (fp = 3.5) gain 1, 0 ON OFF 1.8 - 3.4 1.6 (state 3) (fp = 2.4) 1, 1 ON ON 1 - 3.7 2.7 (state 4) (fp = 1.8) Frequency (GHz) reconfigured frequencies and bidirectional radiation pattern is Figure 8. Measured gain plot of the antenna. obtained in the all switching states of antenna. The following Fig. 8 shows the cumulative gain plot of the proposed antenna’s four switching states. It is inferred that the antenna presents a positive gain in operating frequency bands all the states. In state 1, the maximum gain of 2.5 dB is obtained at the frequency of 4.5 GHz. Similarly, in the state 2 and state 3, a gain of 2.7 dB and 1.9 dB is obtained at 3.5 GHz and 2.4 GHz, respectively. Where, in 4th state a peak gain of 1.6 dB at 1.8 GHz and a moderate gain of 0.7 dB at 3.5 GHz is obtained. The obtained gain values for the four switching states of the antenna are as given in Table 3. Where, the Fig. 9 shows the current distribution in antenna switching from state 1 to state 4. In switching state 3 (D1-ON; D2-OFF), the majority of the current flow is distributed in the lower side of the circular ring patch antenna. In state 4 (D1-ON; D2-ON) the current in concentrated both in the outer and inner ring of the antenna.

Table 3. Maximum gain obtained at each switching state Figure 9. Current distribution :(a) state 1,(b) state 2,(c) state 3, and Switching states Peak gain (d) state 4. State 1 2.5 dB at 4.5 GHz 5. RF ENERGY HARVESTING State 2 2.7 dB at 3.5 GHz This Novel experimental setup is made as shown in the State 3 1.9 dB at 2.4 GHz Fig. 10 (a) to scavenge the various ranges of ambient RF State 4 1.6 dB at 1.8 GHz energy and can act as a permanent energy harvesting resource for the low power VLSI devices. Due to the variation in current distribution different Compared to the existing harvesting technologies, this frequency reconfiguration is obtained.

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REFERENCES 1. Shah, S.A.A.; Khan, M.F. ; Ullah, S. & Flint, J.A. Design of a multi-band frequency reconfigurable planar using truncated ground plane for Wi-Fi, WLAN and WiMAX applications. In IEEE International (a) Conference on Open Source Systems and Technologies (ICOSST), 2014, pp. 151-155. doi: 10.1109/ICOSST.2014.7029336 2. Sulakshana, Chilukuri & Lokam Anjaneyulu. Reconfigurable antennas with frequency, polarization, and pattern diversities for multi- wireless applications. Int. J. Microwave Wireless Technol., 2017, 9(1), 121- 132. doi: 10.1017/S1759078715000926 3. Zhang, Jian; Yang, Xue-Song; Li, Jia-Lin & Wang, Bing-Zhong. Triangular patch yagi antenna with reconfigurable pattern characteristics.App. Computational Electromagnetics Soc. J., 2012, 27(11), 918-924. 4. Costantine, Joseph; Youssef, Tawkb & Christos, G. Christodoulouc. Reconfigurable antennas and their applications. In Handbook of Antenna Technologies, Springer, Singapore, 2015. pp. 1-30. (b) doi: 10.1007/978-981-4560-75-7_61-1 Figure 10. RF energy harvesting module: (a) Block diagram of 5. Arun, V. & Karl Marx, L.R. Micro-controlled tree IoT based reconfigurable ring antenna and (b) Testing shaped reconfigurable patch antenna with RF-energy setup. harvesting. Wireless Personal Commun., 2017, 94(4), 2769-2781. proposed IOT controlled reconfigurable antenna module doi: 10.1007/s11277-017-3975-z tunes to the appropriate frequency band available in that zone. 6. Yang, Xiaofan; Yao, Chen; Longfang, Ye; Manxi, Wang; The complete module has been fixed and tested in the open Min, Yu & Qing, Huo Liu. Frequency reconfigurable area of a building terrace in the range of 25 m away from the circular patch antenna using PIN diodes. In IEEE mobile phone tower (GSM 1800) is shown in Fig. 10 (b). International Conference on Microwave and Millimeter With the help of DC to DC booster (LTC3105) circuit, the Wave Technology (ICMMT), 2016, 2, pp. 606-608. harvested energy from the antenna is rectified and boosted. doi: 10.1109/ICMMT.2016.7762382 Finally, a constant 5 V output is obtained from this embedded 7. Onodera, Shoichi; Ryo, Ishikawa; Akira, Saitou & module. Kazuhiko, Honjo. Multi-band reconfigurable antennas embedded with lumped-element passive components and 6. CONCLUSIONs varactors. In IEEE Microwave Conference Proceedings This novel frequency reconfigurable ring antenna with (APMC), 2013 Asia-Pacific, pp. 137-139. IoT based controlled switch for wireless communication is doi: 10.1109/APMC.2013.6695216 presented. The importance of these techniques is that the total 8. Christodoulou, Christos G.; Youssef Tawk; Steven A. reconfigurable antenna setup is monitored and controlled from Lane & Scott R. Erwin. Reconfigurable antennas for the remote in anywhere worldwide. The switching provided wireless and space applications. In Proceedings of the by NodeMCU with PIN diodes (SOD323) has high isolation IEEE, 100(7), pp. 2250-2261. and also high voltage interference with antenna radiation is doi: 10.1109/JPROC.2012.2188249 eliminated. Switching bands of 4.5 GHz, 3.5 GHz, 2.4 GHz 9. Genovesi; Simone; Agostino, Monorchio; Michele, and 1.8 GHz are attained in each states of 1st, 2nd, 3rd and 4th Borgese Borgese; Sara, Pisu, & Fabio, Michele Valeri. state respectively. This prototype reached a maximum gain of Frequency-reconfigurable with biasing 2.7 dB in 3.5 GHz, 2.5 dB in 4.5 GHz, 1.9 dB in 2.4 GHz, network driven by a PIC microcontroller. IEEE Antennas and 1.6 dB in 1.8 GHz. Bidirectional radiation pattern is Wireless Propag. Lett., 2012, 11, 156-159. attained in all condition and shows a positive gain response doi: 10.1109/LAWP.2012.2185673 throughout its operating frequency band. This reconfigurable 10. Pal, Heena & Choukiker, Yogesh Kumar. Design of antenna can work on different wireless standards like GSM frequency reconfigurable antenna with ambient RF- 1800, DCS 1900, ISM Band, Wi-Fi, Bluetooth, 4G (LTE), energy harvester system. In International Conference Wi-Max, WLAN and some of Satellite Frequency bands. A On Information Communication and Embedded System constant 5 v is obtained with the RF harvesting module in (ICICES2016), India, 2016, 2(1), 1-5. 1800 MHz band. doi: 10.1109/ICICES.2016.7518857 11. Sun, Hucheng; Yong-xin, Guo; Miao, He & Zheng, Zhong.

570 Arun & Marx : Internet of Things Controlled Reconfigurable Antenna for RF Harvesting

A dual-band using broadband yagi CONTRIBUTORS for ambient RF power harvesting. IEEE Antennas Wireless Propag. Lett., 2013, 12, 918-921. Mr Arun V. received his Graduation and Post-graduation in doi: 10.1109/LAWP.2013.2272873 Electronics and Communication Engineering from Anna University, 12. Balanis, A. Handbook of antenna theory, analysis and India, in 2008 and 2010, respectively. Currently pursuing his design. Ed. 3. Wiley publications 2010. PhD in Anna University, India. Presently working as an Assistant Professor at Electronics and Communication Engineering 13. Zeroday. A lua based firmware for wifi-soc esp8266. Department, Anna University – Chennai, Regional Campus Github. Madurai, India.His research interests include: Reconfigurable 14. Wiguna, Hari. NodeMCU LUA Firmware : antenna and RF microwave communication systems. Hackaday. In the current study, he designed the novel antenna structure, 15. Arun, V.; KarlMarx, L.R.; Kumar, Jegadish K.J. & simulated in HFSS and fabricated the prototype. He programmed Christy, Vimilitha C. N-shaped frequency reconfigurable the NodeMCU controller for the testing purpose. He performed antenna with auto switching unit. Appl. Comput. the RF Energy scavenging in the outdoor testing setup. Electromag. Society J.. 2018, 33(6), 710-713. 16. lee, K.F.; Luk, K.M. &Dahele, J.S. Characteristics of Dr L.R. Karl Marx received his BE from Madurai Kamarajar University, India and ME from Thapar Institute of Engineering the equilateral triangular patch antenna. IEEE Trans. and Technology, India, and PhD from National Institute of Antennas Propag., 1988, 36(11), 1510-1518. Technology Trichy, India, in 1988, 2000, and 2011, respectively. doi: 10.1109/8.9698 Presently working as an Associate Professor at Thiagarajar College of Engineering. His research interest includes : Design of actuators, microstrip antennas, microwave sensors, RFID antennas for readers and tags, embedded system. In the current study, he gave the idea for the design of novel antenna structure, simulation in HFSS and fabrication in the prototype. He also gave the idea for choosing the NodeMCU for controlling and testing purpose. He modelled the outdoor experimental test setup.

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